1. Field of the Invention
The present invention relates to a method of placing a bottom block for supporting a workpiece in a manner spaced apart from an upper surface of a table, a block-transferring tool and a machine tool provided with the tool.
2. Description of Related Art
In a machine tool, a to-be-machined article, i.e., a workpiece has been conventionally required to be placed slightly apart from an upper surface of a table when a bottom area of the workpiece is machined.
This will be explained with reference to FIGS. 17A and 17B. In FIG. 17A, a workpiece 100 is placed directly on an upper surface of a table 28. Accordingly, when a bottom A area of the workpiece 100 is machined by a blade 200 of a tool 201 attached to a spindle 30 of a machine tool, the blade 200 damages the upper surface of the table 28. For this reason, the bottom A area of the workpiece 100 cannot be machined.
Consequently, as shown in FIG. 17B, a bottom block 60 is placed under the workpiece 100, whereby the workpiece 100 is slightly lifted apart from the upper surface of the table 28. With this arrangement, even when the bottom A area of the workpiece 100 is machined, the upper surface of the table 28 is not damaged by the blade 200 of the tool, 201.
As a device for placing a workpiece in such a manner, i.e., in a manner so as to lift and support the workpiece apart from the upper surface of the table, a device with use of air pressure (see Document 1: JP-A-2000-219308) is known. However, since such a device needs a complicated structure, a hard block is generally placed under the workpiece.
Herein, such a block to be used under the workpiece is referred to as a “bottom block,” most of which in use are made of metal, particularly iron. This is because metal, particularly iron is advantageous for obtaining various shapes of the bottom block. The shapes of the bottom block may take a variety of shapes, e.g., solid, hollow, frame-shaped, box-shaped, stick-shaped, plate-shaped, rail-shaped, T-slotted and the like.
However, when the bottom block as described above is placed on the upper surface of the table, large working load is imposed on an operator and handling of the bottom block is extremely difficult due to, a heavy weight of the bottom block. Moreover, the bottom block needs to be lifted up by a crane or the like when being placed, which causes danger to the operator due to a fall of the bottom block, or damage on the upper surface of a machine table, damage on the bottom block per se or the like. Accordingly, prevention of such danger to the operator, prevention of machinery damage, prevention of damage on the bottom block per se and the like have been desired. In addition, improvement in accuracy of placement position and, eventually, improvement in productivity by an advanced automatic setting of the bottom block have been requested.